1. Field of the Invention
The present invention relates to polarized electromagnetic relays and in particular to such relays having a one-piece coil core body having a hollow interior with a movable ferromagnetic contact element disposed in the interior of the body.
2. Description of the Prior Art
A polarized electromagnetic relay is known, for example, from German AS No. 27 23 220, which corresponds to U.S. Pat. No. 4,215,329, having a one-piece coil body about which an electromagnetic coil is wound which has a hollow tube-like interior in which a movable ferromagnetic contact element is disposed substantially parallel to the longitudinal axis of the coil body. The contact element is fastened at one end to a carrier which is received in grooves of the coil body parallel to the coil axis and has an opposite free end which is movable between two angled pole plates associated with a permanent magnet, the pole plates being held in a flange of the coil body by means of a plug-type connection.
Relays constructed in the manner described above provide a very high grade relay which achieves a good closing of the permanent magnetic circuit as well as a good connection of the control flux circuit by virture of the end-face coupling of the permanent magnet to the pole pieces and further by means of additional flux guidance tabs which are carried on the pole pieces. The carrier for the movable contact element inside the coil body is an elongated adjustment plate which can be deformed for adjusting the movable contact element by means of an externally applied magnetic field after the relay has been hermetically sealed such as, for example, by casting.
Relays of this type have the disadvantage that all parts of the relay within the protective housing of the relay must be hermetically sealed therein by casting. Moreover, a special device for generating magnetic pulses and for the measurement of the various armature positions resulting from such pulses is necessary for step-by-step magnetic adjustment of the movable contact element. The development of such special devices may be uneconomical in those instances in which the demands made on the relay insofar as contact tolerances are not especially high, and also in those instances wherein a relatively small number of relays are needed.